Calculate modeled photosynthetically active radiation

Calculate photosynthetically active radiation (PAR) for a series of date-times and site coordinates. Input times should be mean solar time, as expected by stream metabolism models.

Usage

calc_light(solar.time, latitude, longitude, max.PAR = 2326)

Arguments

solar.time: POSIXct vector of mean solar time values.
latitude: Numeric. Site latitude in decimal degrees between -90 and 90.
longitude: Numeric longitude in decimal degrees. Western longitudes are negative.
max.PAR: Numeric. Peak daily PAR in umol m^-2 s^-1. Defaults to 2326.

Value

Numeric vector of modeled PAR in umol m^-2 s^-1.

Details

This function was adapted from streamMetabolizer::calc_light and is included here under the terms of the CC0 1.0 Universal public domain dedication, as described at: https://www.usgs.gov/information-policies-and-instructions/copyrights-and-credits

Original citation: Appling, A. P., Hall, R. O., Yackulic, C. B., & Arroita, M. (2018). Overcoming Equifinality: Leveraging Long Time Series for Stream Metabolism Estimation. Journal of Geophysical Research: Biogeosciences, 123(2), 624–645. https://doi.org/10.1002/2017JG004140

Examples

utc <- as.POSIXct("2024-06-21 18:00:00", tz = "UTC")
solar.time <- convert_UTC_to_solartime(utc, longitude = -96.6)

calc_light(solar.time, latitude = 39.1, longitude = -96.6)
#> [1] 2228.291